1. Field of the Invention
The present invention generally relates to semiconductor devices, and, more particularly, to a semiconductor device having high-density external connection electrodes.
In recent years, there has been an increasing demand for semiconductor devices having small packaging surfaces, as electronic apparatuses have been becoming smaller. Semiconductor devices are also expected to have a narrower electrode pitch or external connection terminal pitch.
2. Description of the Related Art
FIG. 1 is a sectional view of a semiconductor device 10 of the prior art.
The semiconductor device 10 has a simple structure comprising a semiconductor chip 1, a resin package 2, metal films 3, and stud bumps 7. The semiconductor chip 1 is connected to the metal films via wires 8. The lower surface of each metal film 3 is arranged on the same plane as the packaging surface 6 of the resin package 2. The resin package 2 covers the semiconductor chip 1, the metal films 3 except the lower surfaces, and the wires 8. The resin package 2 thus protects the semiconductor chip 1, the metal films 3, and the wires 8. A stud bump 7 which serves as a mounting terminal is attached to the bottom surface of each metal film 3.
The stud bumps 7 as the mounting terminals can be arranged at short intervals, and high-density mounting can be achieved accordingly.
When the semiconductor device 10 is mounted on a printed circuit board, the positions of the stud bumps 7 are detected, so that the stud bumps 7 are positioned to connection electrodes formed on the printed circuit board. As shown in FIG. 2A, the stud bumps 7 are irradiated with light, and a CCD camera 9 picks up the reflected light from the stud bumps 7. For ease of explanation, only one stud bump 7 is shown in FIGS. 2A and 2B. The image data picked up by the CCD camera 9 is then processed to detect the positions of the stud bumps 7.
Each of the stud bumps 7 has a bonding portion 7a connected to the corresponding metal film 3, a protruding portion 7b situated on the bonding portion 7a, and a flat top end portion 7c formed at the top end of the protruding portion 7b. The bonding portion 7a and the protruding portion 7b both have a curved exterior. When the stud bumps 7 having the curved exterior are irradiated with light, the light scatters on the curved exterior surfaces of the bonding portions 7a and the protruding portions 7b. As a result, the strength of light received by the CCD camera 9 is reduced.
FIG. 2B shows an image of a stud bump 7 picked up by the CCD camera 9. In this figure, the shaded portion represents where light scattering has occurred. In the case where the stud bumps 7 are used as detection marks for detecting their positions, the picked-up image of each stud bump 7 is too dark to detect, resulting in inaccurate detection of the positions of the stud bumps 7. Such inaccuracy leads to a poor packaging yield of semiconductor devices.
A general object of the present invention is to provide semiconductor devices in which the above disadvantages are eliminated.
A more specific object of the present invention is to provide a semiconductor device, with which the positions of mounting terminals can be accurately detected at a time of mounting, thereby attaining a high packaging yield.
The above objects of the present invention are achieved by a semiconductor device comprising:
a semiconductor chip;
a resin package which encapsulates the semiconductor chip;
mounting terminals formed on a bottom surface of the resin package facing a printed circuit board, the mounting terminals protruding from the bottom surface;
first wires which are connected to the semiconductor chip at one end and are directly connected to the mounting terminals at the other end; and
second wires which are exposed at one end through the resin package so as to form a flat surface with the bottom surface of the resin package.
With the above structure, the exposed portions of the second wires can function as detection marks, and the light reflectance at the detection marks can be made high. Thus, the positions of the detection marks can be accurately detected, and the accuracy in mounting the semiconductor device to a printed circuit board can be improved.
Also, the second wires can be formed at the same time as the wire bonding process of the first wires. Accordingly, the detection marks can be easily formed. Furthermore, the exposed portions of the second wires are used as the detection marks, so that the accuracy in positioning the first wires at the time of mounting the semiconductor device to a printed circuit board can be greatly improved.
The above objects of the present invention are also achieved by a semiconductor device comprising:
a semiconductor chip;
a resin package which encapsulates the semiconductor chip;
mounting terminals formed on a bottom surface of the resin package facing a printed circuit board, the mounting terminals protruding from the bottom surface of the resin package;
wires which are connected to the semiconductor chip at one end, and are connected to the mounting terminals at the other end through first metal films formed on the bottom surface of the resin package; and
second metal films which are exposed through the bottom surface of the resin package.
With the above structure, the exposed second metal films function as detection marks, and the light reflectance at the exposed portions can be improved. Thus, the positions of the detection marks can be accurately detected, and the accuracy in mounting the semiconductor device to a printed circuit board can be improved.
It is difficult for some detection devices to detect circular detection marks such as those formed by the second wires. To avoid such difficulties, the detection marks are formed by the second metal films, which can have any shape such as a rectangular shape, a cross-like shape, or a T-like shape. Thus, the positions of the detection marks can be accurately detected by a detection device that has difficulties in detecting circular objects, and the semiconductor device can be accurately mounted in a predetermined position.
The above objects of the present invention are also achieved by a semiconductor device comprising:
a semiconductor chip;
a resin package which encapsulates the semiconductor chip; and
protruding electrodes as mounting terminals,
wherein the protruding electrodes have flat top end surfaces.
With the above structure, the flat top end surfaces of the protruding electrodes can be used as detection marks. Since the light reflectance at the top ends of the protruding portions is high, the positions of the top ends can be accurately detected. Thus, the accuracy in mounting the semiconductor device to a printed circuit board can be greatly improved.
The above and other objects and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings.